Field of the Invention
This invention relates to portable saws and, more particularly, to a saw having a cutting chain driven by a battery operated motor.
Background Art
Portable saws that utilize a driven cutting chain have been in existence for many decades. In a typical construction, a cutting chain is trained in a track on a cutting bar to move in an endless path. A drive component, which may be in the form of a sprocket or the like, is rotated through a motor to effect driving of the chain.
Chain saws designed for even light, non-professional, use are routinely subjected to heavy loading. Thus, motors for chain saws have generally all been required to generate a relatively high power output.
While battery operated chain saws have been developed over the years, until recently, limitations on battery technology have prevented widespread commercial acceptance of battery operated chain saws as a viable alternative to chain saws with fuel powered engines. Generally, batteries have been deficient in terms of their power output capability as well as their running time between charges. The inability to practically control size and weight of batteries has also impeded the transition from fuel operated chain saws to those powered by batteries.
In recent years, there has been a very dramatic improvement in battery technology that has prompted the use of batteries in a wide range of new product categories, including in chain saws for both non-professional and professional applications. For example, lithium ion battery technology has advanced to the point that compact, relatively lightweight batteries can produce power at levels achievable in the past only through combustion-type engines. This and other advancements in battery technology have led to a very significant industry trend towards supplanting long used lines of chain saws built around combustion engines with those utilizing battery operated drive motors. This trend has been bolstered additionally by the fact that battery operated chain saws have a number of significant functional advantages compared to those built around combustion engines.
Battery operated chain saws generally can operate with less vibration. Battery operated chain saws can also be designed to generate significantly less noise during operation. Importantly, designers of battery operated chain saws do not have to contend with emission control, that has been a vexatious problem, particularly as many jurisdictions adopt increasingly tougher standards for all fuel powered engines.
A major shift in technologies, such as that described above for the chain saw, creates unique challenges for those in this industry. Resources dedicated in the past to highly successful fuel driven products must be diverted to meet anticipated customer demands for battery operated technology. New resources must be allocated for designing, conducting research and development with respect to, and manufacturing, battery operated products. Such a drastic change in direction for some companies may be catastrophic, since they may ultimately be caused to abandon facilities and practices that progressively evolved and were perfected over many decades, and are peculiar to, and not readily adaptable to, the fuel operated model.
Chain saws utilizing combustion engines have heretofore commonly been built around an internal structural frame that results in an endo-skeletal design. That is, the frame is configured to accommodate all of the working components—namely, control boards, oil tanks, fuel tanks, engines, etc.—that are progressively built thereon. Operating handles have been connected to the frame typically through isolation structure that avoids vibration transmission to a user.
On the other hand, the evolving model for battery operated chain saws has predominantly used an exo-skeletal design. That is, the outer housing provides the foundation for the internal components. This model is typical of many battery operated and corded electrical devices that utilize a clam shell configuration.
This latter approach has a number of drawbacks. First of all, the outer housing/frame has a predetermined fixed shape that dictates the end appearance of the chain saw. Little flexibility is allowed in terms of modifying shape or aesthetics. Thus, little flexibility is afforded in differentiating the appearance of products that might have different operating features or capabilities. Essentially, only color and ornamentation, such as decals, are available to effect this differentiation.
Further, an outer frame construction inherently challenges designers to maintain overall structural rigidity, particularly since relatively large loading and impacts are applied to chain saws in their normal operating environment. These forces tend to distort the housing/frame. This distortion may lead to a compromising of the outer housing as well as the internal operating components. A failure of the outer housing may, in a worst case, render the chain saw inoperable and unsalvageable.
As noted above, the new battery operated construction model generally forces personnel involved in all areas of product development, from design to marketing, to learn new processes and techniques. Past engineering practices and techniques, that were applicable to the internal frame construction (endo-skeletal design), may not be usable in a practical sense to design and produce chain saw products with the exo-skeletal design. Further, facilities used to produce fuel powered chain saws may not be practically convertible to allow production of battery powered chain saws.
Still further, as the transition to battery power is taking place, those in the industry may have to provide large volumes of both battery and fuel driven chain saws to the market. The inability to navigate the transitional period and eventually efficiently offer primarily the battery operated product line, may lead to the decline or outright demise of many heretofore successful enterprises.
In short, the chain saw industry has seen a radical shift in the construction of its product and how that product will be developed, manufactured, and marketed in the future. Entities that do not meet this challenge may face serious economic consequences. Businesses are in need of direction to allow them to meet the above challenges in the rapidly evolving industry which embraces battery technology over the familiar and highly evolved fuel operated engine technology.